In order to produce a semiconductor laser device having a higher power output, a plurality of unit, i.e., individual, semiconductor lasers can be integrated to form a semiconductor laser array device. FIGS. 9(a)-9(c) are sectional views illustrating prior art array type semiconductor laser devices. The device includes unit semiconductor lasers 51, each having an active layer 52 centered between side surfaces of the unit semiconductor laser 51. Reference numeral 3 designates a submount, and numeral 4 designates a wire.
As shown in FIG. 9(a), in an array type semiconductor laser device comprising four unit semiconductor lasers 51, active layers 52 are provided in the respective unit semiconductor lasers with a space of 300 .mu.m between the active layers, i.e., light emitting points, of the adjacent unit lasers. The central points of the active layers 52 have a distribution extending over 900 .mu.m. In this case, it is difficult to focus the emitted light on a narrow region using an optical system, such as a lens.
As shown in FIG. 9(b), in an array type semiconductor laser device comprising four unit semiconductor lasers 51 that are vertically laminated, when a thickness of each unit semiconductor laser 51 is 100 .mu.m, the region where the light emitting points are distributed (hereinafter referred to as a light emitting region) extends over 300 .mu.m. When the unit semiconductor laser and the submount, or the unit semiconductor lasers are bonded using solder, it is necessary that the melting point of the solder used for each bond be lower as the bonded portion is more distant from the submount so that a bond does not melt in soldering a subsequent unit semiconductor laser above a previous bond. More specifically, it is necessary to use various kinds of solder having different melting points, which complicates the bonding process.
As shown in FIG. 9(c), when the unit semiconductor lasers 51 that are vertically laminated are divided into two columns, the complication of the solder bonding process is relieved. However, assuming that the space between the side surfaces of the respective unit semiconductor lasers in two columns facing each other is about 100 .mu.m and the width of the unit semiconductor laser 51 is about 300 .mu.m, the space between the light emitting points in the horizontal direction becomes about 400 .mu.m, so that the light emitting region is widened to 100 (length).times.400 (width) .mu.m.sup.2 as compared with the structure of FIG. 9(b). Accordingly, it is difficult to focus the emitted light on a narrow region. Although it is thought that the width of the unit semiconductor laser 51 may be narrowed to reduce the size of the light emitting region, a width of 200 .mu.m or more is required to radiate heat sufficiently and facilitate handling. Therefore, there is a limit to reducing this width to narrow the light emitting region.
As described above, in the array type semiconductor laser device divided into two columns, the process for bonding with the solder is simpler than that in the array type semiconductor laser device comprising four unit semiconductor lasers that are vertically laminated. However, the light emitting region is widened, so that it is difficult to collect the emitted light using a lens.